Grade by Grade
B. Number · Operations: Adding, Subtracting and Equal Groups

Operations: Adding, Subtracting and Equal Groups: Unit Review

A1 B2.1 B2.2 B2.3 B2.4 B2.5 B2.6About 40 minutes
Learning goals
  • I can add and subtract facts to 20 and explain my strategy.
  • I can add and subtract two-digit numbers to 100 and check my answer.
  • I can solve story problems and tell if my answer makes sense.
  • I can make equal groups and share things equally.

Words to know

fact family
Adding and subtracting facts that use the same three numbers, like 7 + 8 = 15 and 15 − 8 = 7.
trade (regroup)
Swap 10 ones for 1 ten, or 1 ten for 10 ones.
estimate
A smart guess that is close to the exact answer.
equal groups
Groups that all have the same number of things.
share equally
Give each person or group the same number.

Let's review!

You have learned a lot in this unit: facts to 20, math rules, mental math, estimating, adding and subtracting numbers to 100, story problems, equal groups and fair sharing. This review has a few questions from every lesson. Try each one, then press Show answer to check. If a part feels tricky, go back to that lesson for more practice.

1275whole on top, parts belowOne triangle, four facts:7 + 5 = 125 + 7 = 1212 − 5 = 712 − 7 = 5
A fact triangle for 7, 5 and 12 gives four facts: two adding facts and two subtracting facts.

Adding and Subtracting Are Partners

1

Write the fact family for 6, 9 and 15.

2

Find the missing number: □ − 8 = 5

3

Jon says 14 − 6 = 9. Check by adding. Is he right?

Math Rules: Any Order, Zero and Grouping

1

What is 37 + 0? What is 37 − 37?

2

Solve 3 + 8 + 7 + 2 in a smart way.

3

Is 15 − 5 the same as 5 − 15? Why?

Addition Facts to 20

1

8 + 8 = ? and 8 + 9 = ?

2

9 + 6 = ?

3

7 + 5 = ?

Subtraction Facts to 20

1

13 − 4 = ?

2

18 − 9 = ?

3

12 − 10 = ? and 12 − 9 = ?

Mental Math to 50

1

27 + 20 = ?

2

29 + 6 = ?

3

45 − 18 = ? Explain your strategy.

Estimating Sums and Differences

1

What is the closest ten to 34?

2

Estimate 28 + 19.

3

Ola says 41 − 19 = 32. Use an estimate to check.

Adding Two-Digit Numbers to 100

1

43 + 36 = ?

2

58 + 25 = ?

3

What is 6 tens and 12 ones?

Subtracting Two-Digit Numbers within 100

1

86 − 43 = ?

2

71 − 35 = ?

3

100 − 58 = ?

Solving Story Problems to 100

1

There were 63 children at a winter festival. 28 went home. How many stayed?

2

Some people were on a ferry. 24 more got on. Now there are 60. How many were on at the start?

3

Rosa has 17 more stickers than Adam. Adam has 25. How many stickers does Rosa have?

4

Leah has $30. She gets $25 for her birthday and spends $12 on a puzzle. How much does she have now?

plate 1: 4plate 2: 4plate 3: 412 crackers on 3 platesGroups: 3 groups of 44 + 4 + 4 = 12Sharing: 12 shared by 34 each
The same picture two ways: 3 groups of 4 make 12, and 12 shared among 3 gives 4 each.

Multiplication: Equal Groups

1

How many legs do 4 chairs have, if each chair has 4 legs?

2

An array has 2 rows of 7. How many in all?

3

8 children each eat one half of an orange. How many oranges do they eat?

Division: Sharing Equally

1

Share 12 blueberry muffins equally among 3 friends.

2

10 kids make teams of 2. How many teams?

3

Share 9 pencils equally between 2 kids. How many each? Any left over?

Just for fun

Why is the equal sign so humble?

Because it knows it isn't greater than or less than anybody else!

How to use this review

  • Do the review over two or three short sittings. Each section matches one lesson.
  • Let your child use tools: counters, ten frames, bundles of 10, a number line or drawings. Using tools is part of Grade 2 math.
  • After each answer, ask "How did you know?" or "How can you check?" Explaining matters as much as the answer.
  • Note which section had mistakes, then revisit that lesson's examples, activity and practice.
Check your understanding

Quiz

1.

Which fact is in the same family as 7 + 9 = 16?

2.

What is 4 + 9 + 6?

3.

What is 7 + 8?

4.

What is 15 − 7?

5.

What is 38 + 7?

6.

Which is the best estimate for 52 + 29?

7.

What is 46 + 37?

8.

What is 80 − 34?

9.

A pet store has 3 tanks with 5 fish in each tank. How many fish?

10.

Share 12 grapes equally among 4 children. How many does each child get?

For parents and teachers

Use mistakes to choose what to revisit. Each review section matches one lesson.

  • Can't write fact families, subtracts the wrong way round, or struggles with missing numbers (□ − 8 = 5): revisit Adding and Subtracting Are Partners.
  • Thinks 37 − 0 = 0, always adds left to right, or switches numbers in subtraction: revisit Math Rules: Any Order, Zero and Grouping.
  • Slow with addition facts to 20 or off by one on near doubles: revisit Addition Facts to 20 and play the flash card games.
  • Counts back one at a time for big take-aways, or forgets the second jump through 10: revisit Subtraction Facts to 20.
  • Adds tens to the ones (27 + 20 = 29 or 227), or loses track when crossing a ten: revisit Mental Math to 50 and use a hundred chart.
  • Can't find the closest ten, or doesn't notice an answer that is far off: revisit Estimating Sums and Differences.
  • Writes tens and ones side by side (58 + 25 = 713), or forgets to trade: revisit Adding Two-Digit Numbers to 100 with straw bundles.
  • Subtracts the smaller digit from the bigger in each place (71 − 35 = 44): revisit Subtracting Two-Digit Numbers within 100.
  • Adds every story's numbers, or gets stuck on missing-start or two-step problems: revisit Solving Story Problems to 100 and draw bar models.
  • Adds the two numbers instead of making groups (4 groups of 4 = 8), or confuses halves: revisit Multiplication: Equal Groups.
  • Makes unequal shares or mixes up "how many each" with "how many groups": revisit Division: Sharing Equally with real snacks.

A few mistakes are normal. Praise the strategy your child explains, not only the right answer.